Countersink.



0.0. SKRUKRUD.

COUNTERSINK.

APPLICATION FILED AUG.26| I9l6.

ATTORNEY To all whom t concern: i

- smooth kerf, free from frayed edges. i

Application le August 26, 1916. Serial No. 117,000.

Be it known that I, OLAF O.. Sxmixmn), a citizen of the United States, residing at Lanesboro, in the county of Fillmore\and State of Minnesota, have invented new and useful Countersinks, of which the following. is a'specication. l l

This invention has reference to counter.` sinks, and its object is to provide a countersink attachable to a drill or Aother boring tool, which countersink will produce. a

, In accordance with the present invention there is provided a countersinkjn the form of a block of conoidal shape with cutting. teeth having a pitch opposite tolthat of the flutes of the drill or -other boring tool-that is to say, the trend of said teeth being retrogressive from the larger end to the smaller end with respect to thedirection of active ,rotation of the countersink-so thatv the countersink teeth force the wood fibers, con-l sidering Wood as the material being bored, in the direction ofr travel of the countersink into the wood, this resulting in a smooth edge at -the countersunk' hole, instead of a more or less frayed edge often produced by the ordinary cutting tools due to the forcing of the cuttings or kerf in a direction opposite to that of the travel of the tool into the wood and the intervening grooves between the teeth opening through the upper face of said countersink to prevent choking of the same and permitting the 'free passage of the cuttings from the countersunk. l

The invention will be 'best understood from a consideration ofthe following detailed description, taken in connection with the accompanying drawing, forming part of this specication, with the further understandin that while the drawing shows a practica -form of the invention, the latter is not conned to strict conformity with the showing of the drawing, but may be changed and modied, so long as such changes and .modifications come within the scope of the appended claims.

In the drawing r- Figure l is an elevation of the countersink applied to a twist drill.

Fig. 2 is a longitudinal diametric section of the countersink applied to a twist drill with the latter shown in elevation.

Fi 3 is an elevation of the countersink applied to a twist drill, but related to thel latter to serve as a depth gage.

Specication of Letters Patent.

A circumferential series of cuttinfg respect to t Referring ,to ythe drawing, there is shown I a block l constitutin thebody portion of the countersink, the lock bein shape, .with a flattened apex 2, w ile thesur# face of the conical block is formed into' a teeth or edges 3, having a pitch circum the block and retrogressing from the large end of the block toward the smaller. or flattened end 2i) such retrogression beingwith countersink wheninoperation. Proceeding' from the larger end of the of conical erential of v e direction of rotation of the block 1 is an axially extended neck 4haviiig a screw-threaded hole for the passage-of a 4set screw 6 having a head 7 at one end and the block is a passage 9 for a drill 10, shown i in the drawings as an ordinary-twist drill of the kind employed in metal boring, but it will be understood that `other types of drills or boring toolshfor either. wood or metal'may be used. A twist drill has helically -disposed grooves o iutes 11 therealong havin a p rogressive pitch along the drill from t e butt end ofthe latter toward the drill point, the direction of pitch being forward--or progressing, whilev that-of the teeth 3 of the countersink is. backward or retrogressive with respect to the direction of rotation of the drill and countersink carried thereby.

The neck i has an axial passage 12 therethrough in alinement with the passage 9 and of larger diameter, so that the passage 12 may be considered as a counterbore with respect to the passage 9. Each tooth 3 comprises solely two surfaces outwardly converging to form a knife edge extendin from the smaller to the larger end of the bo y, and

the intervening grooves of the teeth open through the upper face of the block, so that in the working of the countersink the cuttings from the countersunk formed thereby from the countersunk irrespective of the depth of cutting action of the block, thereby preventing the choking of the countersink with the resultant smooth formation o f said `a thickened offset 5 on one side provided with will have free passage through the grooves propriete distance from the active end oi? the drill, so that e hole may loe bored ley the lutter end when the desired depth is reached the countersinlr becomes active in the usuel manner to enlarge the entering end oi the bored hole end shape it in e monner permitting it toy seat e heed or other enlargement upon the device to he introduced into the bored hole. Usually, the countersinh is eniployed to enlarge theentering end of the hole in a manner to receive e screw heed end hence the countersinlr is usually shaped for such e purpose. The countersinlr is held upon the drill. l hy the set screw li? the engeging end S of which may enter one ci the tintes ll close to the point Where the drillY emerges from the passage 9 into counterhore l2.

There ere iorrns et drills designed to en ter adopters Which in'turn are held in e suitable chuclr provided in certain types of tools designed for boring and other like Work. The eountersinlr l2 is provided for the reception of such en adapter, so that the countersink is available for use not only with straight-shank or other twist drills9 but may he used with the type of tools referred to Where adopters are employed to hold the drill to the tool. i

To use the eountersinlr es e depth gege7 it is reversed in position on thedrill, so that the neel; l is toward the active end of the drill, With the free end of the neck toward the active end of the drill and et e distance therefrom corresponding to the depth to which it is desired the drill shall enter the worlr. This arrangement, which is shown in Fig. 3, determines the depth to which the Y drill is permitted to enter the Work, further progress hein stopped hy the engagement of the tree en of the noch e with the Work.

Considering the drill es Working in Wood, the cuttings ci the drill ere directed ley the helical liutee ll toward the entering end of the hole being bored end tend to lift the' monroe grain of the Wood towardsuch entering end or the hole, the result'oiten losing the production of Ymore or less roughness et such entering end, Thecounterslnk l, et course, ohliteretes ein roughness Whichmey here heen produced etfthe entering `end ci the hole, lout if the pitch of the teeth 3 was the saine es the pitch of the ilutes or grooves il, or even if the teeth were parallel With the mis oi rotation of the countersink, `there would still loe roughnessV produced at the outer or large end of the countersunlr hole.` -With the present invention such roughness is obliterated, because the pitch of the teeth 3 isretrogressive and all cuttings `ere directed intorthe countersunlr portion ot the hole, While the trend ot the teeth 3 is into the countersunlr hole.. llhe result is that the groin oit the Wood Yis forced inwardly with respect to the materiel heing operated upon and ell iraying of the edges is effectively prevented.

What is claimed is le` ,one-piece countersinh, comprising nbody portion or head ot conoidel form centrally bored to receive e, hit, and e circuler series of angularly disposed teeth with e Y retrogressive pitch or trend from the larger end of the hody portion toward the smaller end thereof with respect to the directionV of active rotetion of the countersink and conforinin to the contour of the conoidal shape thereoi, each tooth comprising solely two surfaces outwardly converging to form e, knife edge extending from the smaller to the larger end et the body portion, with the intervening grooves opening through the upper face of seid loody portion.

ln testimony, that l claim the foregoing es my owna l here hereto axed my signeture in the presence of two Witnesses.

@LAF SKRUKR'UD. Witnesses:

l-l. l). @immuni S. Koosn. 

